Greater London · England
External Mastic in Highgate
Sealing brickwork movement joints, render, cladding and façade joints for homeowners, landlords and businesses in Highgate. Fully insured, ARBOMaster approved and guaranteed for a year.
- Panel joints letting water in
- Plants rooting in failed movement joints
- Joints where the bead has come unstuck
Honest limits
To be straight with you, some problems need a different trade:
- Damp that is not coming from the joint
- Loose or hollow render, which needs re-rendering
- Cracked brickwork or render that needs a builder or plasterer
If in doubt, phone 0345 464 0079 or email us and we’ll say what we think before booking.
Where we work in Highgate
- Joints between brick and frames
- Copings & trims
- Render & cladding joints
- Concrete & block
- Brickwork movement joints
- Façade panels
External mastic in Highgate, done properly
External mastic is a job where short cuts show quickly. New sealant over old, joints packed with mortar and beads with no backing rarely last long. We strip the joint back and start again. Typical jobs include weathered mastic that no longer stretches and moss and dirt in joints with no sealant left, across joints between brick and frames, façade panels and brickwork movement joints.
Modern London flats rely on sealed movement joints and cladding joints. Period houses have different weak points, such as gutter joints, trims and the line where an extension meets the old wall, and both kinds of building are found across London.
We guarantee the work for a year. If something is not right with it in that time, tell us and we’ll put it right.
- Location
- Highgate (N6, N19, NW5)
- Region
- Greater London
- Cover
- 12 months on all our work
- Price
- Quoted before any work starts
- Call
- 0345 464 0079
- Updated
- 26 October 2026
What the job involves on each surface
Render joints
Render is weaker at the surface than brick, so a low-modulus sealant is kinder to the joint edges. Priming is done where the sealant calls for it.
Concrete and blockwork
Concrete and block walls shrink as they dry and move with temperature. Their movement joints are sealed over backing rod with a flexible sealant.
How to look after the new joints
Aftercare is simple:
- Never let anyone fill a movement joint with mortar
- Deal with leaking gutters that soak the joints below
- Ask before painting over external sealant
- Act on the first splits you see
Keep the joints clear of soil, plants and climbing growth. Anything that holds water against the joint wears it out sooner.
Leaks behind façade panels and render often go unseen. By the time there’s a damp patch, the damage can be well established.
What external mastic looks like in Highgate
Compared with the north and west, the South East gets less rain, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. London terraces and converted houses often share gutters, downpipes and walls, so it’s worth agreeing who is responsible before work starts.
Homes close to Highgate United Reformed Church include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move. Rented homes near Upper Holloway station change hands often, and outside joints that have cracked can let damp into a rental, so check them between lets.
Highgate is about 2 miles north-east of Hampstead, in Greater London. Homes, rented property, offices and hotels in Highgate is covered for external mastic, old or new, large or small. The work is guaranteed for a year. Across Greater London, we cover 764 places, and Highgate is one of them.
Postcode districts we cover here for external mastic: N6, N19 and NW5. Streets in the area include Wood Lane, Grange Road and Talbot Road. If you’re just outside Highgate, we cover Upper Holloway (1 mile south-east), Dartmouth Park (1 mile south), Lissenden Gardens (1 mile south), Crouch End (1 mile north-east) and Tufnell Park (1 mile south-east). Within a short drive, we also cover London (5 miles south-east), City of Westminster (4 miles south), Marylebone (4 miles south), Kensington (6 miles south-west), St Pancras (3 miles south) and Shoreditch (4 miles south-east).
Around Highgate
In Highgate, that means homes and buildings near The Angel Inn, St Aloysius RC College and Whittington Park. The closest station to Highgate is Upper Holloway station, about 0.9 miles south-east of the centre. A little further out are Highgate Private Hospital (0.6 miles north-west) and Montfichet's Tower (4.4 miles south-east). Not far away are Darland's Lake and Parkland Walk.
DIY versus a professional finish
Sealing over old silicone is the commonest DIY error. Silicone doesn’t stick to old silicone, so it lifts and traps water and mould underneath. All the old material has to come out first.
If you do try it yourself, take your time over the preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it doesn’t work out, we can still put it right.
How the visit works
A visit follows a simple pattern: we look at the joints together, mask and protect the surrounding surfaces, do the work and tidy away. It usually takes anything from a few hours to several days, depending on the building. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. Mention any building rules, key holders or managing agents when you book.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
Preparing for the visit
- Try not to wet indoor joints just before the visit
- Mention any sign-in or site rules at work premises
- Plan for the work area to be out of bounds to pets and children
Ask for a quote
Need a quote? Please ring 0345 464 0079 or send us an email and tell us about the job. You’ll know what we plan to do, and what it will cost, before any work begins.
Related advice
What affects the cost of external mastic
Some jobs are bigger than they look, and some smaller. The main factors:
- The number and length of the joints
- Any working-time requirements on site
- Access and height
- Whether old sealant or filler has to be cut out
A failed joint rarely gets cheaper to fix by waiting, as water and mould keep getting in. If you are unsure, phone 0345 464 0079 or drop us an email for an honest opinion and a quote.
What to tell us for a quote
To make quoting easier, please include:
- Whether it has been sealed before
- Pictures of the joints, sent by email
- What’s wrong with the joints now
- The address or postcode of the job
A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints, and add photos by email if you can.
Also near Highgate
Other services in Highgate
Do you need external mastic in Highgate?
UV, rain and frost all age exterior sealant. In time it goes hard, crazes on the surface and stops stretching, so the next time the wall moves, it splits or pulls away.
Keep an eye out for any of the following:
- Plants rooting in failed movement joints
- Movement joints with cracked, split or missing sealant
- Sealant pulling away from one side of the joint
- Old sealant gone brittle and cracked
Highgate is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Comparing quotes
- Which sealant they’ll use, and why
- What the quote includes, VAT included or not
- How the colour is chosen
- How much experience the applicator has
Highgate questions
Do you work for landlords with property near Upper Holloway station?
Yes, landlords and agents are among the people we work for. You can ring 0345 464 0079 or email us with the details for a clear quote.
Is Highgate in your area for external mastic?
Yes, Highgate is within the area we cover. Our work covers London and the South East. Just call 0345 464 0079 or email us with a few details of the job, and we’ll give you a clear quote.
Do you seal joints where cladding meets other materials?
Yes. Different materials move at different rates, so a flexible sealant is needed where they meet. We choose one that suits both surfaces.
What do you need from me for a quote?
The location, the problem and the rough size of the job. If you can, email a few pictures.
Is the work guaranteed?
Yes: twelve months. If anything isn’t right with the work within the year, let us know and we will sort it.
What is backing rod for?
Backing rod controls the sealant depth and keeps it off the back of the joint. That way it bonds to the two sides only and can stretch.
How do I get a quote for external mastic in Highgate?
The cost depends on the size of the job, access and how much old sealant has to come out. Call for a quick quote.
Will it make a mess?
Not at all. The area is protected while we work and cleaned up afterwards.